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Using a Fishbone (or Ishikawa) Diagram to Perform 5-why Analysis

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The fishbone (or Ishikawa) diagram is another way to visualize your 5-why analysis, and allows you to classify your analysis into broad categories. Part 3 of a four-part series on five-why.

By Karn G. Bulsuk

More information: An Introduction to 5-why, 5-why Analysis using a Fishbone Diagram and The Weaknesses of 5-Why
The fishbone diagram, also known as the Ishikawa diagram, is another tool to provide you with a visual representation of your 5-why analysis.

The strength of the fish bone diagram is that it allows you to focus on specific cause categories, which may help you to better focus your line of enquiry. In other words, this diagram is similar to a surgical strike, which provides more precision. The table method is like the shotgun approach, in which we think of as many possible causes as possible without a specific path.

In this article, we will be using the same scenario as the table analysis example in the previous article.

An opening tip…

I strongly recommend using paper and pen when you perform the analysis, as it allows you to put your ideas down much quicker than a computer would. I have found that using a computer to create fishbone diagrams actually interrupts the flow of ideas, as it requires fiddling around with text boxes and other unnecessary formatting.

Set up the Fishbone

Firstly, on a sheet of paper, draw a long line with the box at the end. The line represents the spine of the fish. In the box, write down the effect. In this case, it is “Application processing was behind schedule.”

Choose your Cause Categories

You can choose to focus your line of inquiry by choosing a set of cause categories: main topics which you will base your 5-why analysis on. Mio has chosen to focus on methods, management, process and people, since the problem here is related to these four main areas. She has drawn additional lines from the spine and placed boxes containing each individual category.

There are also a whole set of common cause categories, some of which are listed below:

  • 3M’s and P – Methods, Materials, Machinery, and People
  • 4P’s – Policies, Procedures, People and Plant
  • 6M’s – Machine, Method, Materials, Measurement, Man and Mother Nature (Environment)
  • 8P’s – Price, Promotion, People, Processes, Place / Plant, Policies, Procedures & Product (or Service) (recommended for administration and service industry)
  • 4S’s – Surroundings, Suppliers, Systems, Skills (recommended for service industry)
  • Equipment, Process, People, Materials, Environment, and Management

The First Why: Starting your analysis

To figure out why Alencia has so many problems, Mio has decided to first focus on the Methods the company has employed.

From here, the 5-why analysis is applied as usual, and Mio asks herself “In terms of methods, why was application processing behind schedule?”

From her observations, Mio understands that a lot of the statistics used in the company are wrong because many employees are still collecting data and calculating figures using paper and a calculator, before inputting that data into a spreadsheet. A lot of time is wasted double or even triple checking data because it’s unreliable.

As a result, her answer to the first “why” is: Employees used manual calculations, leading to inaccurate data, requiring time to find problems and correct them.

To put it into the fishbone diagram, draw a line branching off from methods, and write the answer at the end of the line.

The Second Why

Mio wants to understand why people do not use the full potential of computers. Her next why therefore focuses on this:

Why question: Why did employees use manual calculations?
Answer: They are unable to use complicated Excel formulas.

A line would branch off from the first why line, and the answer would be written at the end.

The Third Why

Why question: Why were they unable to use complicated Excel formulas?
Answer: Because they lacked Excel training.

The Fourth Why
Why question: Why did they lack Excel training?
Answer: Management assumed that everyone was able to use Excel to its fullest ability, and did not anticipate that there would be a lack of Excel skill.

The Fifth Why

Why question: Why did management not anticipate the lack of skill?
Answer: There was insufficient thought put into long-term planning.

Repeat, Repeat, Repeat

Do the same for each “why” you can come up with, and repeat with each cause category until you complete your diagram.

Cleaning up the diagram

Fishbone diagrams were designed to be done quickly the first time round to ensure the ideas flow smoothly, and so you should clean it up prior to using it for analysis.

Consider the following:
  • Many branches under one category may need further study
  • Few branches under one category may need more analysis
  • If several major categories have only a few branches, they may need to be combined

Using the Diagram to Find the Root Causes

After Mio has finished filling out the diagram, she now can use it to identify root causes. To do so, she needs to identify repetitive root causes that seem to appear over and over again by circling ones which keep appearing. She notices that a lack of training and a lack of marketing on the benefits of a software solution are two root causes that keep appearing.

Mio’s Conclusion

In her report, Mio concludes that:

“A lack of awareness of the advantages of a software solution and buy-in, coupled with insufficient training on existing software solutions are two of the leading and fixable root causes.”

Another tip

In the event that your diagram becomes unwieldy and has so many branches in one cause category, you can split that cause into its own fishbone diagram. In the following example, Mio split the “people” cause category into its own set.

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  • 枫叶情 said:  

    Thank you for the notes. I was struggling with my case study.

  • Karn G. Bulsuk said:  

    No problems! I'm glad it helped!

    Best wishes


  • RDQuick said:  

    This is exceptional. I have never seen a fishbone diagram used with the 5 why process. It makes perfect sense and this is an easy method to train employees how to use the fishbone diagram.
    Thanks for the tip!

  • Karn G. Bulsuk said:  

    Hi RDQuick

    Thanks for dropping by. It's good to know you found it useful!

    Best wishes


  • Anonymous said:  

    Hi Karn,

    This is the first time I learnt to use Fish bone analysis...

    Thanks for making it simple...

    Best regards,

    Sameer K

  • Karn G. Bulsuk said:  

    Hi Sameer

    No problem! It's good to find that it was useful.



  • Anonymous said:  

    5 why applied to cause and effect. Seriously useful to an old dog trying to learn new tricks !
    many thanks,

  • Karn Bulsuk said:  

    Hi Mel, very glad you found it useful! Let me know if there's anything else you want to see or know.


  • Anonymous said:  

    Hi Karn,

    I came across this site while trying to learn concepts in manufacturing engineering. Really well-explained and simply put. Thankyou very much.



  • Karn Bulsuk said:  

    Hi Sandeep

    It's good to see that the article helped. Thanks for stopping by!


  • Raj said:  

    Very nice article, Thanks very much

  • karnbulsuk said:  

    Thanks for dropping by!

  • DD said:  

    i have a problem on identifying the root cause on my project. i cant go pass the first why. i already has the problem description, and causes made by man, machine, method and materials.

  • karnbulsuk said:  

    Doing 5-whys analysis assumes that you have a decent knowledge of the processes and issues involved. Have you perhaps asked someone else to help you go through this too?

    Alternatively, can you identify what exactly is keeping you from going past the first why?

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